Tri-beta(beta(3,5-di-t-butyl-4-hydroxybenzylthio)alkyl carboxyalkyl) phosphites

ABSTRACT

COMPOUNDS, USEFUL AS STABILIZERS, HAVING THE FORMULA   (3,5-DI((CH3-)3-C-),4-(HO-)PHENYL)-CH2-S-(CH2)N-COO-   (CH2)M-O)3*P   WHEREIN N AND M ARE EACH A POSITIVE INTEGER BETWEEN 1 AND 8; AND N AND M MAY BE EQUAL TO EACH OTHER OR NOT.

United States Patent laims ABSTRACT OF THE DISCLOSURE Compounds, useful as stabilizers, having the formula l Hs)a 3 wherein n and m are each a positive integer between 1 and 8; and n and m may be equal to each other or not.

This application is a division of copending application Ser. No. 684,910, filed Nov. 22, 1967, and assigned to the assignee of the present invention.

This invention relates to novel compounds and to their use as stabilizers for organic materials. More particularly, this invention is concerned with the use of these compounds as stabilizers and antioxidants for olefin polymers and to polymer compositions stabilized therewith.

A rapidly expanding industry utilizing polyolefin resins has created a need for stabilizers that will render the finished articles of manufacture more useful, more versatile in application, and more nearly permanent. Polymers of aliphatic olefins have a combination of properties, such as high resistance to stress cracking, high tensile strength, and stability under load, that makes them useful in the manufacture of pipe, film, wire, coatings, or various molded objects such as bottles and the like.

These polyolefins, however, are subject to considerable degradation at the high temperatures that are required in their processing or that may be encountered by the finished articles. They may also be degraded by chain cleavage resulting from oxidation or attack by acids. The molecular breakdown which occurs in these polymers during fabrication is usually evidenced by increased brittleness at low temperature and reduced tensile strength and dielectric properties.

It is customary to incorporate small amounts of stabilizers in the polymer to improve the resistance thereof of thermal and oxidative degradation, such as various amines, diaryl sulfides, phenolic compounds, organic phosphites, and the like. Many of the known stabilizers, how ever, do not provide the required stabilizing eifect, while others impart undesired color to the stabilized compositions.

In accordance with this invention, it has been found that a variety of organic materials can be stabilized against thermal and oxidative degradation by incorporating into the polymer composition a small amount of a compound having the formula iJa 3 wherein n and m are each a positive integer between 1 and 8; n and m may be equal to each other or not. The re- Patented June 8, 1971 ice sulting stabilized compositions can be processed under conditions of elevated temperature and mechanical working without substantial increase in the melt flow rate and without important color change.

Specific examples of the stabilizers of this invention include such compounds as tri-,8[/i'(3,5-di-t-butyl-4-hydroxybenzylthio) ethyl carboxyethyl] phosphite having the a formula l C( a)a Other stabilizer compounds useful for this purpose are tri-fl[B(3,5-di-t-butyl-4-hydroxybenzylthio) ethyl carboxy- [propyl]phosphite and tri-p[B(3,5-di-t-butyl-4-hyrodoxybenzylthio)ethyl carboxybutyl] phosphite.

The materials with which this invention will be illustrated are normally solid homopolymers and copolymers of aliphatic olefins having from 2 to 8 carbon atoms per molecule, such as ethylene, propylene, 1-butene, isobutylene, 2-butene, l-pentene, and l-hexene, and mixtures thereof.

In general the amount of agent to be added to the polyolefin depends upon the degree and kind of stabilization desired. The amount of antioxidant can vary from about 0.001 to about 5.0 percent, based on the weight of the polyolefin, with amounts of approximately 0.05 to 0.5 percent being preferred. As a rule, it is preferred to use the minimum amount required to achieve the desired results.

The compounds of this invention can be mixed with the polyolefin in any suitable manner that will effect thorough distribution and dispersion. This can be accomplished in equipment suitable for mixing solids, as by milling the polyolefin with the additive on heated rolls such as are used in the compound of rubber or on other suitable milling or mixing equipment, such as for example a Banbury mixer or conventional rubber mill. Instead of adding the stabilizing agent to the polymer in the solid or molten state, it can be added to a solution or suspension of polymer in an organic solvent or to an aqueous dispersion thereof and the volatile solvent subsequently removed by vaporization.

The antioxidants of this invention may be supplemented by small amounts of finely dispersed particles of carbon black to shield the polyolefin from the deleterious degradative effects of ultraviolet radiation, thereby improving its resistance to light deterioration. Carbon black suitable for use herein includes both activated and unactivated types, such as channel carbon black, furnace carbon black, animal or vegetable carbon black, thermal carbon black, light lamp blacks, acetylene blacks, and the like, and carbon blacks activated in the presence of such materials as oxygen, sulfur, or selenium. The average particle size of carbon black used herein should be below about 1,000 angstroms and preferably below about 200 angstroms, so as to ensure a uniform dispersion of the carbon black through the polymer. Amounts of carbon black within the range of about 0.05 to 5.0 percent by weight of the polymer, and preferably about 0.1 to 3.0 percent, are satisfactory. For some polyethylene application, carbon black concentrations of up to about 50 percent by Weight can be present, especially where partially conductive polyethylene-carbon black compounds are employed.

The preparation of the novel stabilizers and their use in polyolefin resin compositions are illustrated by the examples which follow. It is to be understood, however, that these examples are given solely for the purpose of illustration and that the invention is not to be regarded as being limited to any of the specific materials or conditions recited therein except as set forth in the appended claims.

istics for the physical properties of the polymer; the carbonyl values, the holding of the chemical properties.

EXAMPLE II Melt index (MIm) ater Percent of :0 after- 30 60 90 180 5 30 60 90 180 DTA, mins. mins. mins. mins. mins. mins. mins. mins. mins. mins. mins.

Sample A 5. 6 5. 6 5. 6 3.5 018 O18 018 018 02 2. 0 B 2.8 4.3 4.7 5.1 .013 .14 .16 .23 .70 1

di-tFbutyl-4-hydroxybenzylthio) ethylcarboxyethyl] phosphite.

2 B=Polyethylene with no sta lizer.

EXAMPLE I Into a dry l-liter 3-necked flask equipped-with a stirrer, thermometer, N inlet, additional funnel, and reflux condenser protected with drying tubes was placed 58.0 grams of hydroxyethy(3,5 di t butyl-4-hydroxybenzylthiopropionate) (0.157 M) and 19 grams of N,N-dimethylaniline (0.157 M) in 200 ml. of dry benzene. The mixture was cooled to 15 C., and while being stirred a solution of 7.1 grams of phosphorous trichloride (0.052 M) in 50ml. of benzene was slowly added. The reaction was exothermic, and the temperature was held at -15 C. When addition was completed, the flask was stirred for 3 hours at room temperature and then the amine salt was removed by filtration. The filtrate was evaporated to yield an almost colorless thick oil, identified as tri-B[/3(3,5-di-tbutyl-4-hydroxybenzylthio) ethyl carboxyethyl phosphite.

Analysis.Calcd for C H O S P (percent): C, 63.57; H, 8.27; S, 2.70; P, 8.49. Found (percent): C, 64.86; H, 8.67; S, 2.50; P, 7.67.

A satisfactory antioxidant should hold the chemical and physical properties of the original organic material during an accelerated oxidation testing procedure, generally up to three hours duration. For the following examples, the test procedure consisted of milling one pound of polyethylene in air on a two roll laboratory mill having a front roll speed of 25 r.p.m. and a back roll speed of 35 r.p.m. with the distance between the two rolls adjusted to maintain a uniform rolling back in the nip and a mill temperature of 320 F. After the polymer started to melt, 300 p.p.m. of the antioxidant was added. Samples (75 grams) were taken after 5, 30, 60, 90 and 180 minutes, and melt index, weight percent carbonyl, and oxidation induction time were determined. Oxidation induction time was determined by differential thermal analysis (DTA), indicating The analysis measures the length of time before oxidation starts. The melt index demonstrates the holding character- :P L C a)a J;

wherein n and m are each a positive between 1 and 8; and n and m may be equal to each other or not.

2. Tri ,8[ 3(3,5-di-t-butyl-4-hydroxybenzylthio) ethyl carboxyethyl] phosphite.

References Cited UNITED STATES PATENTS 3,351,680 11/1967 Gutman et al. 260-948 3,408,324 10/1968 Braus et a1 260948X CHARLES B. PARKER, Primary Examiner R. L. RAYMOND, Assistant Examiner US. Cl. X.R. 26045 .95 

